Laundry standpipe drain could be fixed with adapter

We moved into our 1999 home just over a year ago and have already had problems with our basement washing machine clogging and spilling water onto the floor from the point where the machine's drain hose empties into the wall drain.

Roto-Rooter told us that lint clogs the pipe where the water drains from the machine and nothing can be done other than to have them come out to clear the clog. Apparently this problem began before we moved here. Is there anything we can do to prevent the lint from clogging the drain pipe?

I'm surprised that lint could clog a 2-inch ABS drainpipe. Since it took about a year for the clog to build up, indications are that a nail or some type of construction material may have fallen into the standpipe during construction and landed in the P-trap. It most likely is not lodged in the P-trap because the snake gets past it but it may be resting at the bottom where it could catch lint. The obvious approach is to check inside the P-trap by removing it (if it's removable) or cutting it off (if it's not). If the pipes are concealed in a finished wall, the wall will have to be opened up for this procedure.

However, thanks to your photos, I spot a copper pipe (not sure of its size or if it's rigid or soft) coming out of the far side of the standpipe about an inch or so above the P-trap. It appears that there is caulk around the copper pipe where it enters the ABS pipe. I also see that the basement is unfinished and the pipes are exposed, which will make the project easier.

This tells me two things. First, the copper pipe acts as a trap primer by feeding water to the P-trap in a nearby floor drain. Also, an improper fitting was used to attach the copper pipe to the standpipe. Most likely the copper pipe protrudes into the standpipe where it catches lint yet permits the snake to get past it.

Because the Uniform Plumbing Code (UPC) requires that all floor drains be primed, water must be supplied to the P-trap to keep the trap filled with water. If the trap goes dry, then sewer gases could enter the home. One way to prime a floor drain is to use an actual trap primer valve, which would tap a nearby cold water line for its water supply. The second method, as shown in your photo, is to tap into the washing machine standpipe. Every time the washer discharges water, the water swirls around inside the standpipe and the primer outlet captures some of it for the floor drain's P-trap.

The improper fitting in your standpipe could be corrected by using an ABS tapped P-trap adapter also known as a "PPA" (Precision Priming Adapter). It's also known generically as a "BAP" adapter after the name of its first manufacturer.

Both the trap primer (P1 and P2) and Precision Priming Adapter are manufactured by Precision Plumbing Products, Inc. and can be found under "Products" and then "Trap Primers" at their web site www.pppinc.net.

The PPA adapter can be purchased off the Internet or from a contractor's plumbing supply house and comes in two models to accommodate either 3/8-inch (1/2-inch o.d.) or 1/2-inch (5/8-inch o.d.) copper tubing.

A brass compression fitting on one side of the PPA adapter accepts the copper primer line. The entire unit then fastens to the inside of a 2-inch, 3-inch, or 4-inch ABS fitting or coupling with solvent cement. Do not alter or change the compression fitting to accommodate a smaller primer line. Use at least a 3/8-inch (1/2-inch o.d.) primer line and nothing smaller. An undersized primer line could pass completely through the compression fitting and the PPA adapter into the pipe, which would return you to the same situation you are trying to correct.

Installing the correct adapter will give you the opportunity to remove the P-trap and inspect it for foreign material before reassembly. If you experience the same problem a year later, then call in a plumber who works with RIDGID's SeeSnake, rather than Roto-Rooter for another service call.

SeeSnake is diagnostic equipment that has a camera attached to the end of the snake and a pointer receiver. The camera head is inserted into the pipe, and the operator views the inside of the pipe on a small monitor as the camera penetrates the pipe. The pointer receiver picks up signals from a transmitter just behind the camera head and accurately pinpoints both audibly and via a meter screen the center of the pipe and its depth. If there's anything inside the pipe, the SeeSnake will find it.